Fluid zeolite catalyst conversion of alcohols and oxygenated derivatives to hydrocarbons by controlling exothermic reaction heat

ABSTRACT

Alcohols and related oxygenates are converted in a riser reactor and dense fluid catalyst bed (ZSM-5 zeolite catalyst) circulated through a plurality of satellite stripping-cooling zones for temperature control. Catalyst utilized comprises from 5 to 20 weight percent coke for activity and selectivity characteristics promoting the formation of olefins and aromatics at temperatures below about 427° C. (800° F.).

CROSS REFERENCE TO RELATED APPLICATION

This is a Continuation In Part of U.S. Application Ser. No. 89,706,filed Oct. 30, 1979 now U.S. Pat. No. 4,238,631.

BACKGROUND OF THE INVENTION

The application of fluidized catalyst techniques, developed particularlyin the petroleum industry for effecting chemical reaction embodying thedistribution of heat and/or the disposal of undesired heat, has longbeen accepted as a major processing tool of the industry. For example,fluidized catalyst techniques have been particularly useful forcatalytic cracking of oil vapors to produce lower boiling products andregeneration of the catalyst used in such an operation. It has also beenproposed to use the fluidized catalyst technique, primarily for thedisposal of generated heat, in the highly exothermic reactions ofFischer-Tropsch synthesis and the known Oxo process and in other suchexothermic processes. In the fluidized catalyst operations previouslydeveloped, disposal of the reaction heat has been accomplished by manydifferent techniques including transfer of catalyst through coolingsections and/or indirect cooling means with liquids or a fluid catalystto absorb reaction heat transferred directly or indirectly by the finelydivided fluidized catalyst particles. Not only are these prior artcatalyst techniques used for temperature control by addition and/orremoval of heat, but they have also been found useful for maintainingselective conversions and extending the active life of the catalyst usedin the process.

The present invention is concerned with an arrangement of apparatus andmethod of operation employing a fluid catalyst system in which methanoland related oxygenates are converted particularly to dimethyl ether andhydrocarbons in an upflowing catalyst phase system comprising relativelydiluted and more dense phase systems. The exothermic heat of reaction isutilized as hereinafter disclosed to provide product selectivity andprolong the useful life of the catalyst employed in the chemicalconversion operation. U.S. Pat. Nos. considered in the preparation ofthis application include 2,373,008; 3,480,408; 3,969,426; 4,013,732;4,035,430; 4,044,061; 4,046,825; 4,052,479; 4,071,573 and 4,118,431.

SUMMARY OF THE INVENTION

This invention relates to the method and means for effecting selectivechemical reactions in the presence of a catalyst comprising a selectclass of particulate crystalline zeolites. More particularly, thepresent invention is concerned with effecting exothermic chemicalreactions, in the presence of crystalline zeolites of selected crystalarrangement, thereby particularly promoting the formulation ofhydrocarbon product materials higher boiling than the reactant chargematerial. In a more particular aspect, the present invention isconcerned with effecting the conversion of lower alcohols, relatedoxygenates and derivatives thereof in a fluidized mass of catalyticparticulate material comprising a selected class of crystalline zeoliteproviding a pore dimension greater than about 5 Angstroms, pore windowsof a size provided by 10-membered rings of oxygen atoms, asilica/alumina ratio of at least 12 and a constraint index in the rangeof 1 to 12. The present invention is also concerned with an arrangementof apparatus for effecting the catalytic conversion of alcohols andcompounds of carbon and hydrogen, with and without combined oxygen, witha fluid mass of catalyst particles, under temperature restrictedconditions, to achieve high yields of higher boiling hydrocarbons,including gasoline boiling range hydrocarbons.

The present invention is concerned with the conversion of methanol, or amixture of lower alcohols and related oxygenates such as ethers,aldehydes and ketones, in the presence of a special type of zeolitecatalyst maintained in an upflowing fluid condition comprising adispersed catalyst phase riser contact zone discharging into a moredense upflowing fluid mass of catalyst particles. The alcohol-containingfeed, initially charged in liquid and/or vaporous condition, may berelatively pure methanol or other lower alcohol or may comprise an etherderivative thereof as a part of the feed.

In our previous application Ser. No. 89,706, now U.S. Pat. No.4,238,631, we disclosed a method whereby initial conversion of themethanol feed to dimethylether intermediate was carried out to at least70% of theoretical completion prior to passing the reaction mixture tothe second relatively dense fluid mass of catalyst particles for finalconversion thereof to C₁ to C₁₀ hydrocarbons. A method has now beenfound whereby the initial conversion of the methanol-containing feed,that is the conversion carried out in the first relatively dispersedcatalyst phase riser contact zone, may be desirably carried out for atime, temperature and pressure suitable to achieve up to 70% conversionof methanol and other oxygenates in the reactant feed.

BRIEF DESCRIPTION OF THE DRAWING

The drawing is a diagrammatic representation, in elevation, of onearrangement of apparatus for effecting the catalytic conversion of loweralcohols, ether derivatives and related oxygenates in a special fluidcatalyst system to form hydrocarbons, including gasoline boiling rangehydrocarbons and LPG products.

DESCRIPTION OF SPECIFIC EMBODIMENTS

In a particular operation of the apparatus of the invention, a vaporizedmethanol feed, with or without related oxygenates, is mixed with thezeolite catalyst charged to the bottom of the riser contact zone (asmore particularly discussed below) to form a suspension for flowupwardly through the riser. In this dispersed catalyst phase operation,if operating in a vaporized feed mode, it is desirable to restrict thecatalyst charged to the riser to a temperature of about 322° C. (612°F.) while employing a catalyst to feed ratio of about 10 to 1 and, whenemploying a 20 to 1 ratio, the catalyst temperature is preferablyrestricted to about 366° C. (690° F.). If operating in a liquid feedmode, it will be found desirable to employ higher temperatures and/orcatalyst-to-feed ratios. The dispersed catalyst phase suspension ispassed through a riser contact zone of at least 20 feet in length, andmore preferably from 25 feet up to about 70 feet in length, beforeencountering a distributor grid across the bottom of a larger diametermore dense fluid mass of catalyst thereabove. In this arrangement, thereactant residence time in the riser will vary within the processrestrictions herein identified.

It is contemplated providing in the riser contact zone a residence timeof 1 to 10 seconds. In the more dense phase of catalyst thereabove, areactant product residence time in contact with catalyst is within therange of 5 to 80 seconds.

The exothermic operation contemplated within the above operatingconstraints is predicated upon a catalyst concentration within the risercontact zone within the range of 1 to 15 pounds per cubic foot and inthe range of 20 to about 40 pounds per cubic foot in the more densecatalyst bed phase above the grid. A catalyst-reactant temperature riserestriction, not to exceed more than about 90° C. (195° F.) exothermictemperature rise is maintained between the riser suspension inlet andreactant product outlet above the dense fluid bed of catalyst. Thus, thetemperature constraints of the operation are selected to restrict theproduct outlet of the dense fluid bed of catalyst to below 427° C. (800°F.), and preferably the temperature is not substantially above 407° C.(765° F.). The pressure of the operation is maintained low, generallynot above about 4 atmospheres. It is preferred that the reactor pressureat the bottom of the dense bed be restricted to within the range of 2 to2.5 atmospheres.

These conditions allow the conversion of the methanol feed with minimumcontact of methanol with the final desired products. The reaction pathfor methanol conversion to hydrocarbons shows that very high spacevelocities, within the range of about 50 to 200 such as occurs in adilute catalyst phase, causes methanol to be converted to dimethyl etherand water. This conversion is up to about 70% completed before anysignificant quantities of aromatics are formed.

This initial methanol conversion step is important since methanol andaromatics readily combine to form tetramethylbenzene (durene) in greaterthan desirable quantities. This reaction would occur if methanol wereinjected directly into a fluid mass of catalyst characterized by goodbackmixing. The desired hydrocarbon products, preferably comprising C₁₀and lower boiling materials, are obtained usually at the low spacevelocities in the range of 0.5 to 3.0. This is the space velocity rangewithin which the upper or dense catalyst phase bed is operated.

The apparatus of this invention causes a very large portion of themethanol feed to be converted into dimethylether and olefins in a dilutecatalyst phase riser reactor prior to contact with significantquantities of higher boiling materials, including aromatics, and theremaining conversion thereof to desired hydrocarbons in the upper moredense catalyst phase of the reactor arrangement. The disclosed method ofoperation prevents or substantially reduces the occurrence of reactionsproceeding to the formation of substantial amounts of paraffins andaromatics and minimizes back-mixing of the reactant feed with aromaticproducts.

By maintaining a high coke level on the catalyst, in the range of 5 to20 weight percent, and thereby reducing the catalyst activity, olefinsare preferentially produced for a given space velocity under selectedtemperature conditions. The high coke level is maintained by a limitedregeneration of a portion of the catalyst recovered from the reactionzone. Generally speaking, carbon burning can be limited by controllingthe amount of oxygen available to burn the coke on the catalyst. Anytechnique suitable for the purpose may be employed.

The methanol conversion operation of this invention is one whichrequires and is designed to obtain substantial restriction of thereactant vapor bubble growth to low orders of magnitude. Thus, thevapor-catalyst hydraulic relationship in the contact zone is restrictedby baffles, tubes or a combination thereof, or by any other suitableapparatus means therein, which will restrict the free space and providea surface area of the baffles equivalent to a hydraulic diameter not toexceed about 8 inches and preferably not more than about 4 inches.Bubble dispersing means in the catalyst contact zones, and particularlythe dense fluid bed catalyst contact zone, may also be accomplished withsome success with Pall type rings of desired relatively large size,vertically displaced baffle means such as honeycomb sections or portionsthereof permitting transverse flow, sections of Glitsch grid, perforatedpipe sections, and other known baffling means suitable for the purpose.It is particularly desirable, however, to use elongated open or closedend tubes vertically distributed in the most dense fluid bed andperforated in the walls thereof to provide the surface area aboveidentified and transverse flow of catalyst particles in suspension.

The dispersed catalyst phase riser reactor of this invention may be asingle large diameter riser reactor tube. Alternatively, a plurality ofsmaller diameter riser tubes, such as 3 or 4 or more separate risertubes bundled adjacent to one another or separated from one another, asdesired, may be employed in place of a single riser tube. Chargingcatalyst and alcohol reactant in either vapor or liquid form to thebottom of each riser reactor tube to form a suitable suspension may beaccomplished by conventional techniques known in the prior art toprovide an upflowing suspension of the desired particle concentration.

The crystalline zeolites utilized herein are members of a novel class ofzeolite materials which exhibit unusual properties. Although thesezeolites have unusually low alumina contents, i.e. high silica toalumina mole ratios, they are very active even when the silica toalumina mole ratio exceeds 30. The activity is surprising sincecatalytic activity is generally attributed to framework aluminum atomsand/or cations associated with these aluminum atoms. These zeolitesretain their crystallinity for long periods in spite of the presence ofsteam at high temperature which induces irreversible collapse of theframework of other zeolites, e.g. of the X and A type. Furthermore,carbonaceous deposits, when formed, may be removed by burning at higherthan usual temperatures to restore activity. These zeolites, used ascatalysts, generally have low coke-forming activity and therefore areconducive to long times on stream between regenerations by burningcarbonaceous deposits with oxygen-containing gas such as air.

An important characteristic of the crystal structure of this novel classof zeolites is that it provides a selective constrained access to andegress from the intracrystalline free space by virtue of having aneffective pore size intermediate between the small pore Linde A and thelarge pore Linde X, i.e. the pore windows of the structure are of abouta size such as would be provided by 10-membered rings of silicon atomsinterconnected by oxygen atoms. It is to be understood, of course, thatthese rings are those formed by the regular disposition of thetetrahedra making up the anionic framework of the crystalline zeolite,the oxygen atoms themselves being bonded to the silicon (or aluminum,etc.) atoms at the centers of the tetrahedra.

The silica to alumina mole ratio referred to may be determined byconventional analysis. This ratio is meant to represent, as closely aspossible, the ratio in the rigid anionic framework of the zeolitecrystal and to exclude aluminum in the binder or in cationic or otherform within the channels. Although zeolites with a silica to aluminamole ratio of at least 12 are useful, it is preferred in some instancesto use zeolites having substantially higher silica/alumina ratios, e.g.,1600 and above. In addition, zeolites are otherwise characterized hereinbut which are substantially free of aluminum, that is zeolites havingsilica to alumina mole ratios of up to infinity, are found to be usefuland even preferable in some instances. Such "high silica" or "highlysiliceous" zeolites are intended to be included within this description.Also to be included within this definition are substantially pure silicaanalogs of the useful zeolites described herein, that is to say thosezeolites having no measurable amount of aluminum (silica to alumina moleratio of infinity) but which otherwise embody the characteristicsdisclosed.

The novel class of zeolites, after activation, acquires anintracrystalline sorption capacity for normal hexane which is greaterthan that for water, i.e., they exhibit "hydrophobic" properties. Thishydrophobic character can be used to advantage in some applications.

The novel class of zeolites useful herein have an effective pore sizesuch as to freely sorb normal hexane. In addition, the structure mustprovide constrained access to larger molecules. It is sometimes possibleto judge from a known crystal structure whether such constrained accessexists. For example, if the only pore windows in a crystal are formed by8-membered rings of silicon and aluminum atoms, then access by moleculesof larger cross-section than normal hexane is excluded and the zeoliteis not of the desired type. Windows of 10-membered rings are preferred,although in some instances excessive puckering of the rings or poreblockage may render these zeolites ineffective.

Although 12-membered rings in theory would not offer sufficientconstraint to produce advantageous conversions, it is noted that thepuckered 12-ring structure of TMA offretite does show some constrainedaccess. Other 12-ring structures may exist which may be operative forother reasons and, therefore, it is not the present invention toentirely judge the usefulness of a particular zeolite solely fromtheoretical structural considerations.

Rather than attempt to judge from crystal structure whether or not azeolite possesses the necessary constrained access to molecules oflarger cross-section than normal paraffins, a simple determination ofthe "Constraint Index" as herein defined may be made by passingcontinuously a mixture of an equal weight of normal hexane and3-methylpentane over a sample of zeolite at atmospheric pressureaccording to the following procedure. A sample of the zeolite, in theform of pellets or extrudate, is crushed to a particle size about thatof coarse sand and mounted in a glass tube. Prior to testing, thezeolite is treated with a stream of air at 540° C. for at least 15minutes. The zeolite is then flushed with helium and the temperature isadjusted between 290° C. and 510° C. to give an overall conversion ofbetween 10% and 60%. The mixture of hydrocarbons is passed at 1 liquidhourly space velocity (i.e., 1 volume of liquid hydrocarbon per volumeof zeolite per hour) over the zeolite with a helium dilution to give ahelium to (total) hydrocarbon mole ratio of 4:1. After 20 minutes onstream, a sample of the effluent is taken and analyzed, mostconveniently by gas chromatography, to determine the fraction remainingunchanged for each of the two hydrocarbons.

While the above experimental procedure will enable one to achieve thedesired overall conversion of 10 to 60% for most zeolite samples andrepresents preferred conditions, it may occasionally be necessary to usesomewhat more severe conditions for samples of very low activity, suchas those having an exceptionally high silica to alumina mole ratio. Inthose instances, a temperature of up to about 540° C. and a liquidhourly space velocity of less than one, such as 0.1 or less, can beemployed in order to achieve a minimum total conversion of about 10%.

The "Constraint Index" is calculated as follows: ##EQU1##

The Constraint Index approximates the ratio of the cracking rateconstants for the two hydrocarbons. Zeolites suitable for the presentinvention are those having a Constraint Index of 1 to 12. ConstraintIndex (CI) values for some typical materials are:

    ______________________________________                                                               C.I.                                                   ______________________________________                                        ZSM-4                    0.5                                                  ZSM-5                    8.3                                                  ZSM-11                   8.7                                                  ZSM-12                   2                                                    ZSM-23                   9.1                                                  ZSM-35                   4.5                                                  ZSM-38                   2                                                    ZSM-48                   3.4                                                  TMA Offretite            3.7                                                  Clinoptilolite           3.4                                                  Beta                     0.6                                                  H-Zeolon (mordenite)     0.4                                                  REY                      0.4                                                  Amorphous Silica-Alumina 0.6                                                  Erionite                 38                                                   ______________________________________                                    

The above-described Constraint Index is an important and even criticaldefinition of those zeolites which are useful in the instant invention.The very nature of this parameter and the recited technique by which itis determined, however, admit of the possibility that a given zeolitecan be tested under somewhat different conditions and thereby exhibitdifferent Constraint Indices. Constraint Index seems to vary somewhatwith severity of operation (conversion) and the presence or absence ofbinders. Likewise, other variables such as crystal size of the zeolite,the presence of occluded contaminants, etc., may affect the constraintindex. Therefore, it will be appreciated that it may be possible to soselect test conditions as to establish more than one value in the rangeof 1 to 12 for the Constraint Index of a particular zeolite. Such azeolite exhibits the constrained access as herein defined and is to beregarded as having a Constraint Index in the range of 1 to 12. Alsocontemplated herein as having a Constraint Index in the range of 1 to 12and therefore within the scope of the defined novel class of highlysiliceous zeolites are those zeolites which, when tested under two ormore sets of conditions within the above-specified ranges of temperatureand conversion, produce a value of the Constraint Index slightly lessthan 1, e.g. 0.9, or somewhat greater than 12, e.g. 14 or 15, with atleast one other value within the range of 1 to 12. Thus, it should beunderstood that the Constraint Index value as used herein is aninclusive rather than an exclusive value. That is, a crystalline zeolitewhen identified by any combination of conditions within the testingdefinition set forth herein as having a Constraint Index in the range of1 to 12 is intended to be included in the instant novel zeolitedefinition whether or not the same identical zeolite, when tested underother of the defined conditions, may give a Constraint Index valueoutside of the range of 1 to 12.

The novel class of zeolites defined herein is exemplified by ZSM-5,ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-38, ZSM-48 and other similarmaterials.

ZSM-5 is described in greater detail in U.S. Pat. Nos. 3,702,886 andU.S. Pat. No. Re. 29,948. The entire descriptions contained within thosepatents, particularly the X-ray diffraction pattern of therein disclosedZSM-5, are incorporated herein by reference.

ZSM-11 is described in U.S. Pat. No. 3,709,979. That description, and inparticular the X-ray diffraction pattern of said ZSM-11, is incorporatedherein by reference.

ZSM-12 is described in U.S. Pat. No. 3,832,449. That description, and inparticular the X-ray diffraction pattern disclosed therein, isincorporated herein by reference.

ZSM-23 is described in U.S. Pat. No. 4,076,842. The entire contentthereof, particularly the specification of the X-ray diffraction patternof the disclosed zeolite, is incorporated herein by reference.

ZSM-35 is described in U.S. Pat. No. 4,016,245. The description of thatzeolite, and particularly the X-ray diffraction pattern thereof, isincorporated herein by reference.

ZSM-38 is more particularly described in U.S. Pat. No. 4,046,859. Thedescription of that zeolite, and particularly the specified X-raydiffraction pattern thereof, is incorporated herein by reference.

ZSM-48 can be identified, in terms of moles of anhydrous oxides per 100moles of silica, as follows:

    (0-15)RN:(0-1.5)M.sub.2/n O:(0-2)Al.sub.2 O.sub.3 :(100)SiO.sub.2

wherein:

M is at least one cation having a valence n; and

RN is a C₁ -C₂₀ organic compound having at least one amine functionalgroup of pK_(a) ≦7.

It is recognized that, particularly when the composition containstetrahedral, framework aluminum, a fraction of the amine functionalgroups may be protonated. The doubly protonated form, in conventionalnotation, would be (RNH)₂ O and is equivalent in stoichiometry to 2RN+H₂O.

The characteristic X-ray diffraction pattern of the synthetic zeoliteZSM-48 has the following significant lines:

    ______________________________________                                        Characteristic Lines of ZSM-48                                                d (Angstroms)    Relative Intensity                                           ______________________________________                                        11.9             W-S                                                          10.2             W                                                            7.2              W                                                            5.9              W                                                            4.2              VS                                                           3.9              VS                                                           3.6              W                                                            2.85             W                                                            ______________________________________                                    

These values were determined by standard techniques. The radiation wasthe K-alpha doublet of copper, and a scintillation counter spectrometerwith a strip chart pen recorder was used. The peak heights, I, and thepositions as a function of 2 times theta, where theta is the Braggangle, were read from the spectrometer chart. From these, the relativeintensities, 100 I/I_(o), where I_(o) is the intensity of the strongestline or peak, and d (obs.), the interplanar spacing in A, correspondingto the recorded lines, were calculated. In the foregoing table therelative intensities are given in terms of the symbols W=weak, VS=verystrong and W-S=weak-to-strong. Ion exchange of the sodium with cationsreveals substantially the same pattern with some minor shifts ininterplanar spacing and variation in relative intensity. Other minorvariations can occur depending on the silicon to aluminum ratio of theparticular sample, as well as if it has been subjected to thermaltreatment.

The ZSM-48 can be prepared from a reaction mixture containing a sourceof silica, water, RN, an alkali metal oxide (e.g. sodium) and optionallyalumina. The reaction mixture should have a composition, in terms ofmole ratios of oxides, falling within the following ranges:

    ______________________________________                                        REACTANTS     BROAD        PREFERRED                                          ______________________________________                                        Al.sub.2 O.sub.3 /SiO.sub.2                                                                 = 0 to 0.02  0 to 0.01                                          Na/SiO.sub.2  = 0 to 2     0.1 to 1.0                                         RN/SiO.sub.2  = 0.01 to 2.0                                                                              0.05 to 1.0                                        OH.sup.- /SiO.sub.2                                                                         = 0 to 0.25  0 to 0.1                                           H.sub.2 O/SiO.sub.2                                                                         = 10 to 100  20 to 70                                           H.sup.+ (added)/SiO.sub.2                                                                   = 0 to 0.2   0 to 0.05                                          ______________________________________                                    

wherein RN is a C₁ -C₂₀ organic compound having amine functional groupof pK_(a) ≦7. The mixture is maintained at 80°-250° C. until crystals ofthe material are formed. H⁺ (added) is moles acid added in excess of themoles of hydroxide added. In calculating H⁺ (added) and OH values, theterm acid (H⁺) includes both hydronium ion, whether free or coordinated,and aluminum. Thus aluminum sulfate, for example, would be considered amixture of aluminum oxide, sulfuric acid, and water. An aminehydrochloride would be a mixture of amine and HCl. In preparing thehighly siliceous form of ZSM-48 no alumina is added. Thus, the onlyaluminum present occurs as an impurity in the reactants.

Preferably, crystallization is carried out under pressure in anautoclave or static bomb reactor at 80° C. to 250° C. Thereafter, thecrystals are separated from the liquid and recovered. The compositioncan be prepared utilizing materials which supply the appropriate oxide.Such compositions include sodium silicate, silica hydrosol, silica gel,silicic acid, RN, sodium hydroxide, sodium chloride, aluminum sulfate,sodium aluminate, aluminum oxide, or aluminum itself. RN is a C₁ -C₂₀organic compound containing at least one amine functional group ofpK_(a) ≦7, as defined above, and includes such compounds as C₃ -C₁₈primary, secondary, and tertiary amines, cyclic amine (such aspiperidine, pyrrolidine and piperazine), and polyamines such as NH₂-C_(n) H_(2n) -NH₂ wherein n is 4-12.

The original cations can be subsequently replaced, at least in part, bycalcination and/or ion exchange with another cation. Thus, the originalcations are exchanged into a hydrogen or hydrogen ion precursor form ora form in which the original cation has been replaced by a metal ofGroups II through VIII of the Periodic Table. Thus, for example, it iscontemplated to exchange the original cations with ammonium ions or withhydronium ions. Catalytically active forms of these would include, inparticular, hydrogen, rare earth metals, aluminum, manganese and othermetals of Groups II and VIII of the Periodic Table.

It is to be understood that by incorporating by reference the foregoingpatents to describe examples of specific members of the novel class withgreater particularity, it is intended that identification of the thereindisclosed crystalline zeolites be resolved on the basis of theirrespective X-ray diffraction patterns. As discussed above, the presentinvention contemplates utilization of such catalysts wherein the moleratio of silica to alumina is essentially unbounded. The incorporationof the identified patents should therefore not be construed as limitingthe disclosed crystalline zeolites to those having the specificsilica-alumina mole ratios discussed therein, it now being known thatsuch zeolites may be substantially aluminum-free and yet, having thesame crystal structure as the disclosed materials, may be useful or evenpreferred in some applications. It is the crystal structure, asidentified by the X-ray diffraction "fingerprint", which establishes theidentity of the specific crystalline zeolite material.

The specific zeolites described, when prepared in the presence oforganic cations, are substantially catalytically inactive, possiblybecause the intra-crystalline free space is occupied by organic cationsfrom the forming solution. They may be activated by heating in an inertatmosphere at 540° C. for one hour, for example, followed by baseexchange with ammonium salts followed by calcination at 540° C. in air.The presence of organic cations in the forming solution may not beabsolutely essential to the formation of this type zeolite; however, thepresence of these cations does appear to favor the formation of thisspecial class of zeolite. More generally, it is desirable to activatethis type catalyst by base exchange with ammonium salts followed bycalcination in air at about 540° C. for from about 15 minutes to about24 hours.

Natural zeolites may sometimes be converted to zeolite structures of theclass herein identified by various activation procedures and othertreatments such as base exchange, steaming, alumina extraction andcalcination, alone or in combinations. Natural minerals which may be sotreated include ferrierite, brewsterite, stilbite, dachiardite,epistilbite, heulandite, and clinoptilolite.

The preferred crystalline zeolites for utilization herein include ZSM-5,ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-38, and ZSM-48, with ZSM-5 beingparticularly preferred.

In a preferred aspect of this invention, the zeolites hereof areselected as those providing among other things a crystal frameworkdensity, in the dry hydrogen form, of not less than about 1.6 grams percubic centimeter. It has been found that zeolites which satisfy allthree of the discussed criteria are most desired for several reasons.When hydrocarbon products or by-products are catalytically formed, forexample, such zeolites tend to maximize the production of gasolineboiling range hydrocarbon products. Therefore, the preferred zeolitesuseful with respect to this invention are those having a ConstraintIndex as defined above of about 1 to about 12, a silica to alumina moleratio of at least about 12 and a dried crystal density of not less thanabout 1.6 grams per cubic centimeter. The dry density for knownstructures may be calculated from the number of silicon plus aluminumatoms per 1000 cubic Angstroms, as given, e.g., on Page 19 of thearticle ZEOLITE STRUCTURE by W. M. Meier. This paper, the entirecontents of which are incorporated herein by reference, is included inPROCEEDINGS OF THE CONFERENCE ON MOLECULAR SIEVES, (London, April 1967)published by the Society of Chemical Industry, London, 1968.

When the crystal structure is unknown, the crystal framework density maybe determined by classical pycnometer techniques. For example, it may bedetermined by immersing the dry hydrogen form of the zeolite in anorganic solvent which is not sorbed by the crystal. Or, the crystaldensity may be determined by mercury porosimetry, since mercury willfill the interstices between crystals but will not penetrate theintracrystalline free space.

It is possible that the unusual sustained activity and stability of thisspecial class of zeolites is associated with its high crystal anionicframework density of not less than about 1.6 grams per cubic centimeter.This high density must necessarily be associated with a relatively smallamount of free space within the crystal, which might be expected toresult in more stable structures. This free space, however, is importantas the locus of catalytic activity.

Crystal framework densities of some typical zeolites, including somewhich are not within the purview of this invention, are:

    ______________________________________                                                     Void       Framework                                                          Volume     Density                                               ______________________________________                                        Ferrierite     0.28 cc/cc   1.76 g/cc                                         Mordenite      .28          1.7                                               ZSM-5, -11     .29          1.79                                              ZSM-12         --           1.8                                               ZSM-23         --           2.0                                               Dachiardite    .32          1.72                                              L              .32          1.61                                              Clinoptilolite .34          1.71                                              Laumontite     .34          1.77                                              ZSM-4 (Omega)  .38          1.65                                              Heulandite     .39          1.69                                              P              .41          1.57                                              Offretite      .40          1.55                                              Levynite       .40          1.54                                              Erionite       .35          1.51                                              Gmelinite      .44          1.46                                              Chabazite      .47          1.45                                              A              .5           1.3                                               Y              .48          1.27                                              ______________________________________                                    

When synthesized in the alkali metal form, the zeolite is convenientlyconverted to the hydrogen form, generally by intermediate formation ofthe ammonium form as a result of ammonium ion exchange and calcinationof the ammonium form to yield the hydrogen form. In addition to thehydrogen form, other forms of the zeolite wherein the original alkalimetal has been reduced to less than about 1.5 percent by weight may beused. Thus, the original alkali metal of the zeolite may be replaced byion exchange with other suitable metal cations of Groups I through VIIIof the Periodic Table, including, by way of example, nickel, copper,zinc, palladium, calcium or rare earth metals.

In practicing a particularly desired chemical conversion process, it maybe useful to incorporate the above-described crystalline zeolite with amatrix comprising another material resistant to the temperature andother conditions employed in the process. Such matrix material is usefulas a binder and imparts greater resistance to the catalyst for thesevere temperature, pressure and reactant feed stream velocityconditions encountered in many cracking processes.

Useful matrix materials include both synthetic and naturally occurringsubstances, as well as inorganic materials such as clay, silica and/ormetal oxides. The latter may be either naturally occurring or in theform of gelatinous precipitate or gels including mixtures of silica andmetal oxides. Naturally occurring clays which can be composited with thezeolite include those of the montmorillonite and kaolin families, whichfamilies include the sub-bentonites and the kaolins commonly known asDixie, McNamee-Georgia and Florida clays or others in which the mainmineral constituent is halloysite, kaolinite, dickite, nacrite oranauxite. Such clays can be used in the raw state as originally mined orinitially subjected to calcination, acid treatment or chemicalmodification.

In addition to the foregoing materials, the zeolites employed herein maybe composited with a porous matrix material, such as alumina,silica-alumina, silica-magnesia, silica-zirconia, silica-thoria,silica-beryllia, and silica-titania, as well as ternary compositions,such as silica-alumina-thoria, silica-alumina-zirconia,silica-alumina-magnesia and silica-magnesia-zirconia. The matrix may bein the form of a cogel. The relative proportions of zeolite componentand inorganic oxide gel matrix, on an anhydrous basis, may vary widelywith the zeolite content ranging from between about 1 to about 99percent by weight and more usually in the range of about 5 to about 80percent by weight of the dry composite.

The present invention is concerned with an arrangement of apparatus andthe method of using catalyst of selected activity therein for effectingthe exothermic conversion of hetero type compounds, ethers and carbonylcompounds with a fluid mass of catalyst particles in a mannerparticularly promoting and selecting the formation of olefinic,paraffinic, naphthenic and aromatic compounds. More particularly, thepresent invention is concerned with a method and systems employed fordispersing the exothermic heat of chemical reaction, generated in thepreparation of the above components and related compounds, by contactinga fluidized catalyst comprising a ZSM-5 crystalline zeolite with one ormore reactants selected from the group consisting of alcohols, ethers,carbonyl compounds, and mixtures thereof.

Referring now to the drawing by way of example, a reactor arrangement isshown comprising a lower riser section 2 in open communication with thebottom of a larger diameter vessel 4 containing a relatively dense fluidbed of catalyst 6 having an upper interface 8. A distributor grid 10 ispositioned across the lower bottom portion of vessel 4 and above theoutlet of riser 2. Riser section 2 may comprise more than one separateriser, as mentioned above. There may be a plurality of separate riserconduits within riser 2 such as two, three or four risers, eachseparately fed with reactant feed and catalyst. In the specificarrangement of the drawing a fluid suspension of catalyst in methanolvapors is formed in the bottom portion of riser 2. Catalyst is chargedto the lower portion of riser 2 by "U" bend transfer conduits 12 and12'. In a preferred alternative embodiment, "U" bend transfer conduits12 and 12' may instead comprise inclined conduits containingconventional slide-type catalyst control valves. The feed is charged tothe bottom of the riser by inlet means 14 and 14' communicating with aninverted pan 16 open in the bottom thereof. The vaporous feed thusintroduced mixes with introduced catalyst to form a suspensionthereafter passed through the riser. Catalyst mass 6 is filled with aplurality of vertical elongated tubes 18 provided with openings in thewall thereof to restrict bubble growth within the fluid catalyst bed 6as herein provided.

In the arrangement of the drawing, a reactant material such as methanol,or one comprising methanol and ether, is charged in vaporous conditionto the bottom of riser 2 by conduits 14 and 14' at a temperature ofabout 121° C. (250° F.) to about 260° C. (500° F.) for admixture withcooled and stripped recycled catalyst charged by conduits 12 and 12'. Asuspension mix temperature in the range of 301° C. (574° F.) to 351° C.(664° F.) is formed with the adjusted recycled catalyst and chargedvaporous reactant for passage upwardly through the riser represented byriser 2 in essentially a dispersed catalyst phase condition within therange of 1 to 15, and preferably from 2 to 5, pounds of catalyst percubic foot. The upflowing suspension in the riser section is maintainedunder operating conditions to achieve up to 70% conversion of chargedmethanol or other oxygen-containing reactants in the feed before passingthrough distributor grid 10 and into the bottom of the more dense fluidmass of catalyst 6 thereabove. Completion of the reactions to obtainmore than two-carbon bonded hydrocarbons is accomplished within thedense fluid catalyst bed 6 so that, desirably, at least 99.5% ofmethanol in the feed is converted to a hydrocarbon product comprising C₁to gasoline boiling range hydrocarbons without exceeding an uppertemperature limit of about 399° C. (750° F.) to about 427° C. (800° F.)and preferably not above about 407° C. (765° F.). Cyclone separationequipment (not shown) is provided in the upper portion of vessel 4 toeffect recovery of entrained catalyst particles from reaction products.Products of reaction are recovered from the vessel by conduits 20 forseparation and recovery in downstream equipment (not shown) for therecovery of gasoline boiling range hydrocarbons.

Catalyst is withdrawn from bed 6 by conduits 22 and 22' for transfer anddownflow through catalyst stripping and cooling chamber 24 and 24'.Baffles (not shown) may or may not be employed in an upper portion ofchamber 24 and 24' and above indirect heat exchange means 26 and 26'providing high temperature steam positioned in a lower bottom portion ofchamber 24 and 24'. Stripping gas, such as steam and preferably recyclegas obtained from the process, is charged to vessel 24 and 24' byconduits 28 and 28' respectively. The stripping gas is preferablyintroduced below heat exchange means 26 and 26' for stripping thecatalyst cooled to a desired temperature and before withdrawal from thestrippers. The stripping gas passes generally upwardly through vessels24 and 24', countercurrent to downflowing catalyst, for the recovery bydisplacement of strippable hydrocarbons and particularly aromatics fromthe catalyst at a controlled temperature suitable for recycle to riser2. Stripped products and stripping gas are removed by conduits 30 and30' for passage to the dispersed catalyst phase 5 of vessel 4 andremoval after cyclone separation (not shown) with reaction products byconduit 20. The stripped catalyst, essentially free of aromatics, passesdownwardly through steam developing indirect heat exchange means 26 and26', during which time the catalyst temperature is reduced to a levelsuitable for charging to the base of riser 2, as above discussed, andforming a suspension temperature in riser 2 as defined above. Thepartially cooled catalyst passes from the bottom of strippers 24 and 24'by conduits 12 and 12' communicating with the lower portion of riser 2as "U" shaped catalyst transfer conduits.

A portion of the catalyst inventory is withdrawn from a bottom portionof bed 6 into a catalyst withdrawal well, provided in the vessel abovegrid 10, and thence by conduit 32 provided with flow control valve 34for catalyst regeneration. Generally, the volume of catalyst withdrawnby conduit 32 will be from about 5% to 10% per hour of the totalcatalyst in the system. The catalyst withdrawn by conduit 32 is passedto the base of a riser 36 wherein it is mixed with a transport gas orlift gas introduced by conduit 38. The lift gas may be an inert gas orit may be a gas mixture used to effect regeneration of the catalyst by apartial removal of deposited coke. A suspension is thus formed in riser36 and the suspension is passed upwardly through riser 36 intoregeneration zone 40 containing a bed of regenerated catalyst 42. Aregeneration gas of desired oxygen concentration may be added to thebottom of riser 36 or it may be introduced to a bottom portion of bed 42by conduit 44 and provided with a suitable distributing grid withinvessel 40. A CO₂ rich gaseous product of the partial coke burningregeneration operation is recovered from zone 40 by conduit 46 afterpassing through cyclonic separating means (not shown) normally housed inthe upper portion of vessel 40.

Regeneration of the catalyst is accomplished at a relatively lowrestricted temperature, generally not substantially above 482° C. (900°F.), and under conditions to achieve only a partial removal of coke orcarbonaceous deposits rather than to provide a clean burned catalyst forthe reasons above expressed. Thus, carrying significant levels of cokeon the catalyst is used in this methanol conversion operation as a meansfor controlling catalyst activity and selectivity characteristics. Suchcoke retention levels include from 5% to 20% by weight of coke oncatalyst. In view of the temperature restrictions in bed 6 of reactor 4,it is necessary to pass a relatively low temperature catalyst of highresidual coke from regenerator 40 to catalyst bed 6 by conduits 48 and48'. On the other hand, regenerated catalyst may be passed directly tostripper 24 for flow downwardly therethrough together with catalystpassed thereto by conduit 22 and thus returned to the circulatingcatalyst system.

The reactor system above described may comprise more than the twocatalyst stripping-cooling zones 24 and 24' shown. In fact, it iscontemplated providing four or more of such catalyst stripping-coolingzone arrangements connected to a riser reaction zone to control acommercial system within the limits herein defined.

For example, at a LHSV of 1.0 and 12% coke by weight on the catalyst, 7%by weight of C₂ to C₅ olefins are produced. Lowering the coke levelincreases catalyst activity and, at the same space velocity, a lowerproportion of C₂ to C₅ 's would remain, that is, more olefins would beconverted to aromatics and paraffins.

By maintaining high coke level to produce olefins, the conversion of theformed C₃ -C₅ olefins and isoparaffins produced into additional gasolinein a downstream alkylation unit is enhanced. This further conversion ofolefins results in a higher 9-10 RVP gasoline yield.

In the apparatus arrangement of this invention, the pressure instripper-cooling chambers, and thus the upper level of catalyst retainedtherein, is controlled by gaseous stripping material withdrawal conduits30 and 30' which in turn are provided with pressure contact valves 50and 50'. Thus the pressure at the bottom of the stripping-coolingchamber is equivalent to the pressure maintained in the dispersedcatalyst phase of reactor chamber 4 plus the head of pressure developedby the dense bed of catalyst in vessel 4 through withdrawal conduit 22and 22' and the dense bed of catalyst 23 and 23' extending downwardlythrough vessels 24 and 24'. Valves 52 and 52' are for the purpose ofshutting off the flow of catalyst from the bottom of vessels 24 and 24'.Some additional head of pressure is developed in conduits 12 and 12' toat least the bottom of the "U" bend of the catalyst transfer conduit.

The flow of catalyst from the bottom of the "U" bend upwardly thereininto the riser reactor 2 for admixture with reactant is controlled bycharging gaseous material into the upflowing catalyst by conduits 15 and15'. The gaseous material charged by conduits 15 and 15' may be inert tothe reactions desired or may be hydrocarbon gaseous products of thereaction. Alternatively, the gaseous material thus charged may comprisemethanol-containing feed otherwise charged by conduits 14 and 14' to theriser.

It will be recognized by those skilled in the art that, as mentionedabove, instead of employing "U" bend catalyst transfer conduits, one mayuse straight sloping standpipes communicating with the bottom of riser2. In this arrangement, catalyst flow control valves will be locatedadjacent the bottom of the standpipe. In this embodiment, the methanolreactant will be charged to the bottom of the riser. This slopingstandpipe riser arrangement with feed charged to the bottom of the riserwill be generally similar to that shown for the catalyst regenerationarrangement employing standpipe 32, valve 34, riser 36 and gaseousmaterial inlet 38. Of course, there would be a sloping standpipe fromeach stripping-cooling vessel communicating with the bottom section ofthe riser reactor.

The apparatus of the invention contemplates relatively high catalystcirculation rates through the stripping-cooling zones as well as througha plurality of cyclone separators in the upper dispersed catalyst phaseof reactor vessel 4. Although not specifically shown, it is contemplatedemploying from 6 to 8 combinations of 3-stage cyclones to achieveseparation of catalyst particles from reaction products. Separatedcatalyst will be returned to the lower bottom portion of bed 6, butabove grid 10, by cyclone diplegs suitable for the purpose.

To facilitate distribution of the suspension across the bottom of grid10 following traverse of riser section 2, a plurality of divergingconical shaped baffles 54, coaxially aligned with the riser andpositioned within one another, are provided above the riser outlet inthe dish shaped bottom section of vessel 4. The distributed suspensionpasses through grid 10 and into the bed of catalyst for flow upwardlytherethrough about the gas bubble restricting baffles 18 discussedabove.

Having thus generally described the apparatus and its method ofoperation for upgrading feeds comprising lower alcohols and derivativesthereof, and described specific embodiments in support of thedisclosure, it is to be understood that no undue restrictions are to beimposed by reasons thereof except as defined by the following claims.

We claim:
 1. A method for converting reactants comprising lower alcoholsand related oxygenates to C₁₀ and lower boiling hydrocarbon compounds,including LPG and gasoline boiling range components, whichcomprises:passing a suspension of vaporized reactant material and fluidcatalyst particles comprising a crystalline zeolite materialcharacterized by a silica to alumina mole ratio of at least 12 and aconstraint index of within the approximate range of 1-12 upwardlythrough a relatively dispersed catalyst phase riser contact zone for atime, temperature and pressure suitable to achieve up to 70% conversionof methanol in the reactant feed; passing the suspension comprisingproducts of reaction upwardly through a relatively dense fluid mass ofcatalyst particles for a residence time and temperature sufficient toachieve a total conversion of alcohol in the feed equivalent to at least90% and produce simultaneously a product mixture of C₁ to C₁₀hydrocarbons comprising paraffins, olefins, and aromatics; passingcatalyst withdrawn from a lower portion of said relatively dense fluidmass of catalyst particles downwardly through a plurality of separatecatalyst stripping-cooling zones of desired temperature restriction andthence to the riser reactor for admixture with charged vaporousreactant; passing stripped products from the stripping-cooling zone intoadmixture with product mixture above said more dense fluid mass ofcatalyst and withdrawing reaction products separated from said catalystfrom an upper portion of said reaction zone.
 2. The method of claim 1wherein the exothermic temperature rise of said conversion in said riserand said relatively dense fluid mass of catalyst is restricted tomaintain a dispersed phase temperature above said dense fluid mass ofnot more than 427° C.
 3. The method of claim 2 wherein said dispersedphase temperature is restricted not to exceed 407° C.
 4. The method ofclaim 1 wherein the catalyst to reactant ratio of the initially formedsuspension in the riser is within the range of 10/1 to 20/1.
 5. Themethod of claim 1 wherein the relatively dense fluid mass of catalyst isprovided with vertically extending baffle means arranged to restrict thevaporous catalyst mixture passing upwardly therethrough to a hydraulicdiameter within the range of 4 to 8 inches.
 6. The method of claim 1wherein a portion of the circulated catalyst is withdrawn, subjected topartial regeneration, and thereafter returned to the circulated catalystinventory, and the catalyst charged to the riser contains in from about5 to about 20 weight percent coke on the catalyst.
 7. The method ofclaim 1 wherein catalyst circulation through the riser, dense fluid massof catalyst thereabove and the stripper-cooling zone is in response tothe reactant feed rate and the catalyst pressure at the base of acatalyst transfer zone in communication with said riser reaction zone.8. The method of claim 1, 2, 3, 4, 5, 6 or 7 wherein said zeolite ischosen from the group consisting of ZSM-5, ZSM-11, ZSM-12, ZSM-23,ZSM-35, ZSM-38 and ZSM-48.
 9. The method of claim 8 wherein said zeoliteis ZSM-5.
 10. The method of claim 8 wherein said zeolite additionallycomprises a binder therefor.
 11. The method of claim 1 wherein saidreactants comprise methanol.
 12. The method of claim 1 wherein saidreactants comprise dimethyl ether.
 13. The method of claim 1 whereinsaid reactants comprise a mixture of lower alcohols and ethers.
 14. Themethod of claim 1 wherein said reactants comprise a mixture of loweralcohols and aldehydes.
 15. The method of claim 1 wherein said reactantscomprise a mixture of lower alcohols and ketones.
 16. The method ofclaims 2 or 3 wherein the residence time in the riser contact zone is 1to 10 seconds.
 17. The method of claims 2 or 3 wherein the residencetime in the relatively dense fluid mass of catalyst particles is 5 to 80seconds.